Understanding valve seals

SGBARRACUDA said

Absolutely, that is a good place to start. at a minimum a compression test. What do the plugs look like? oil fouled or? The different valve stem height would have stopped me from installing them.

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compression test checked out. All cyl. btwn 135-145. Plugs look good. I could go out and get a leak gauge set..might be quickest diagnosis. From what I read..
no more than 20% leakdown is acceptable..air @ intake=int. valve, @exh=exh. valve, @ dipstick=rings, @radi=head gskt. The other thing is I haven't beat on it much, but they are iron rings.
As far as stem seals...are the Vitron positive stop seals the ones most use here? The ones with the spring around the top of the seal? Any Manuf. recommendations?
Thanks for the help!